基于中空三棱柱透镜测量液相的扩散系数

介绍了利用中空三棱柱液柱透镜同时测量透明液相折射率和扩散系数的实验方法.获得三棱柱液柱透镜中液相扩散层的光束折射到光屏上形成的折射率分布曲线,计算得出液体的折射率,并求得待测液体的浓度,再根据菲克第二定律在一维无限长扩散下的解,最终计算得到2 mol/L盐水在纯水中的扩散系数D=1.50×10^(-3) mm^(2)/s,与参考值相近.

Measurement of Liquid Diffusion Coefficients of Aqueous Solutions of Glycine, L-Alanine, L-Valine and L-Isoleucine by Holographic Interferometry

The diffusion coefficients of aqueous solutions ofglycine, L-alanine, L-valine and L-isoleucine at 298.15 K were determined by holographic interferometry with accuracy and promptness while without disturbance. The density and viscosity of these solutions were also determined. According to original Gordon model, a model for correlating the diffusion coefficients of amino acids in aqueous solutions was developed and applied. The results showed that this model provided significant convenience in correlation of diffusion coefficients for amino acids system.

Intradiffusion, density and viscosity studies in binary liquid systems of acetylacetone + DMF/DMSO/benzene at 303.15 K and 333.15 K

Intradiffusion coefficients of acetylacetone(AcAc) and DMF/DMSO/benzene in binary systems over the entire concentration range at 303.15 K were determined by 1H diffusion-order spectroscopy(DOSY) nuclear magnetic resonance(NMR) method based pulse field gradient(PFG).The densities and viscosities of the above three binary systems at 303.15 K were also studied and employed to calculate the excess molar volumes(V^E) and deviations in viscosity(△η).Besides,experiments were carried out at 333.15 K for the system of AcAc+DMF.The solvent and temperature effect upon the difference in D between enol and keto tautomers,the tautomeric equilibrium and excess properties(V^E and △η) were discussed as well.Isotherms of V^E as a function of mole fraction of AcAc(χ_1) show positive deviations in benzene but negative deviations in DMF and DMSO,whereas isotherms of △ηas a function of χ_1 record positive deviations in DMF but negative in benzene and DMSO.V^E values show more negative and △η values are less positive in the system of AcAc+DMF at 333.15 K compared to 303.15 K.The V^E and △η were fitted to a Redlich-Kister type equation and the measured results were interpreted concerning molecular interactions in the solutions.

Hydrodynamic dispersion of reactive solute in a Hagen–Poiseuille flow of a layered liquid

An analysis of the solute dispersion in the liquid flowing through a pipe by means of Aris–Barton's ‘method of moments', under the joint effect of some finite yield stress and irreversible absorption into the wall is presented in this paper. The liquid is considered as a three-layer liquid where the center region is Casson liquid surrounded by Newtonian liquid layer. A significant change from previous modelling exercises in the study of hydrodynamic dispersion, different molecular diffusivity has been considered for the different region yet to be constant. For all time period, finite difference implicit scheme has been adopted to solve the integral moment equation arising from the unsteady convective diffusion equation. The purpose of the study is to find the dependency of solute transport coefficients on absorption parameter, yield stress, viscosity ratio, peripheral layer variation and in addition with various diffusivity coefficients in different liquid layers. This kind of study may be useful for understanding the dispersion process in the blood flow analysis.

Investigation on characteristics of liquid self-diffusion in slit nanopores using simple quasicrystal model of liquid

Dynamical properties of liquid in nano-channels attract much interest because of their applications in engineering and biological systems. The transfer behavior of liquid confined within nanopores differs significantly from that in the bulk. Based on the simple quasicrystal model of liquid, analytical expressions of self-diffusion coefficient both in bulk and in slit nanopore are derived from the Stokes–Einstein equation and the modified Eyring's equation for viscosity. The local self-diffusion coefficient in different layers of liquid and the global self-diffusion coefficient in the slit nanopore are deduced from these expressions. The influences of confinement by pore walls,pore widths, liquid density, and temperature on the self-diffusion coefficient are investigated. The results indicate that the self-diffusion coefficient in nanopore increases with the pore width and approaches the bulk value as the pore width is sufficiently large. Similar to that in bulk state, the self-diffusion coefficient in nanopore decreases with the increase of density and the decrease of temperature, but these dependences are weaker than that in bulk state and become even weaker as the pore width decreases. This work provides a simple method to capture the physical behavior and to investigate the dynamic properties of liquid in nanopores.

Rapid proton diffusion in hydroxyl functionalized imidazolium ionic liquids

There is considerable interest in using ionic liquids(ILs) as protic electrolytes. However, the reported proton transfer rate in ILs is quite slow. In this study, we report functionalizing imidazolium ILs with alcohol hydroxyls, aiming at constructing hydrogen bonding networks in the electrolyte, can stimulate fast proton hopping transfer. For demonstration, the diffusion of proton and Cl. in 1-(3-hydroxypropyl)-3-methylimidazolium tetrafluoroboride(C_3OHmimBF_4) were studied using cyclic voltammetry and potentiostatic method at 30 °C. The diffusion coefficient of proton is about one order of magnitude higher than that of Cl. in the same electrolyte, and about 5 times that of proton in the non-hydydroxyl 1-(butyl)-3-methylimidazolium tetrafluoroboride(BmimBF_4) when normalized to the diffusion coefficients of Cl. in respective ILs. In the meantime, 1H NMR spectra revealed a strong hydrogen bonding interaction between proton and C_3OHmimBF_4 which is absent between proton and BmimBF_4, thus the significantly higher diffusion coefficient of proton in C_3OHmimBF_4 may suggest the formation of effective hydrogen bonding networks, enabling rapid proton hopping via the Grotthuss mechanism.